Japan's government has said that it has no choice but to keep pouring water into reactors at the crippled Fukushima Daiichi nuclear power plant to try to limit a huge meltdown.

Chief Cabinet Secretary Yukio Edano told reporters on March 29 that the practice is "unavoidable" -- despite fears it could cause highly radioactive leaks -- in order to prevent radioactive fuel rods from heating up and drying out. He said the discovery on March 28 of highly radioactive plutonium in soil at the facility was "proof" that the fuel rods had already "melted a bit."

Hidehiko Nishiyama, a spokesman for Japan's Nuclear and Industrial Safety Agency, says efforts are being made to try to contain radioactive water at the facility.

"We are currently packing earth and putting up concrete slabs around the area near the vent of the turbine building where the door has been washed away in the tsunami, and we're doing this in order to prevent the possibility that the water there seeps out to sea," Nishiyama said.

Earlier, Japanese Prime Minister Naoto Kan told a parliamentary committee that his government remained in a "state of maximum alert" about the crisis at the earthquake- and tsunami-stricken nuclear plant. Kan said the situation at Fukushima "continues to be unpredictable.

Efforts to restart the cooling systems for Fukushima's six reactors continue to be disrupted by leaks of radioactive materials into the air, water, and sea around the plant.

On March 28, officials said highly radioactive plutonium had been detected in soil at the facility.